Hey, what's up....check this site out;
http://www.ritech-systems.com/928/_X__Pipes/_x__pipes.html [/URL]
In the U.K., the system has been well versed out and are made there also. Seems for the most part, the guys pass the UK MOT with this system & CATs. Also in the UK, believe it is much strictor than in CA as one can get an automated ticket just driving downtown and your carbon footprint is over the standards set, and this is caught with the new "Carbon Camera's" mounted over the highways.
Normal "Cat" test in the UK for a non-cat 91GT are 3.5% carbon monoxide (CO) and 1200 ppm Hydrocarbon (HC), go figure hehe. As long as your car can meet the emissions figures in the UK then all is ok, if not then guess what...time to invest again. HOwever in the great US of A, everyone is required to cross their "T's" and dot their I's.
"With Cat" test is (From a forum last May):
Fast idle (2,500 - 3,000 rpm) CO <= 0.2 HC <=200ppm 0.97 <= Lambda <=
1.03
Normal idle (450 - 1,500 rpm) CO <= 0.3
95GTS Auto (M28/50) the figures are:
Fast Idle Test:
CO: Limit 0.3 %vol
HC: Limit 200 ppm
Lambda: Limit 0.95-1.5
Natural Idle Test:
CO: Limit 0.5 %vol
The idle CO for LH models with cats up to '86 is 0.4 -0.8% (before the
cats).
This implies that it should be possible to get a smooth idle with 0.5%.
However, if you are running with an oxygen sensor, you can't adjust it
manually. It may by OK, but if not, you may have to add the adjuster pot
and change the coding plug in order to make it adjustable.
The rules specifically are
Car first used between 1/8/86 and 31/7/92 the test limit is the CO< 3.5% etc
Car first used after 1/8/92 the test limit is the CO< 0.3% etc
One guy has a 92' GTS non-cat with X-pipes and passed the test within the guidelines, however we are comparing apples to oranges in regards to CA vs. UK. Is a bit confusing but the later is a bit better to understand.
Would be interesting to see this figures for CA on the same model & year in comparrison to the UK, anyone?....Hope this helps a bit.